JP7291611B2 - spark plug - Google Patents

Description

The present invention relates to spark plugs.

Conventionally, as a spark plug, a pre-chamber having an injection hole communicating with the main combustion chamber is provided, and an air-fuel mixture is caused to flow into the pre-chamber through the injection hole, and the flame generated in the pre-chamber is passed through the injection hole into the main combustion chamber. There is something to squirt out. For example, Patent Document 1 discloses a configuration in which a large injection hole with a large diameter and a small injection hole with a small diameter are provided as injection holes, and the opening angle between the large injection holes is smaller than the opening angle between the small injection holes. It is In such a configuration, the flames ejected from the large nozzle holes are diffused outward along the bottom surface of the combustion chamber from the central portion of the combustion chamber, and the flames ejected from the small nozzle holes are diffused toward the outer periphery of the main combustion chamber. It aims to completely burn the air-fuel mixture in the combustion chamber.

Japanese Patent Application Laid-Open No. 2001-227344

However, in the configuration disclosed in Patent Document 1, since the ignition energy of the flame ejected from the small nozzle hole is small, further improvement of the combustion speed is required in order to improve the ignitability. On the other hand, if the length of the flame ejected from the injection hole, i.e., the penetration, is increased to improve the combustion speed, the flame collides with the combustion chamber wall surface such as the piston and cylinder liner, increasing cooling loss and igniting. There is a risk of decreased sexuality. Therefore, there is room for improvement in improving ignitability in the main combustion chamber.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide a spark plug capable of improving ignitability.

In one aspect of the present invention, a sub-chamber (2) located on the tip side in the axial direction of the plug, a sub-chamber forming portion (30) forming the sub-chamber (2), and a tip portion (11) in the sub-chamber. a center electrode (10) located at
A plurality of injection holes (35) are formed in the sub-chamber forming portion for communicating the sub-chamber with the main combustion chamber (3),
At least two orifices (351, 352) of the plurality of orifices are in the spark plug (1) with their respective centerlines (L1, L2) crossing each other in the main combustion chamber.

In the spark plug described above, the center lines of the at least two injection holes provided in the sub-chamber forming portion intersect each other in the main combustion chamber. Therefore, the flames ejected from the nozzle holes collide with each other in the main combustion chamber. As a result, flame turbulence in the main combustion chamber becomes greater than when the flames ejected from the respective injection holes are translated in the main combustion chamber. As a result, the area ignited by the flame in the main combustion chamber can be expanded, the combustion speed in the main combustion chamber can be increased, and the ignitability can be improved.

As described above, according to the above aspect, it is possible to provide a spark plug capable of improving ignitability.

It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

2 is a side view of the spark plug in Embodiment 1. FIG. FIG. 2 is a partially enlarged cross-sectional view taken along line II-II in FIG. 1; The bottom view of the spark plug in Embodiment 1. FIG. (a) A bottom view of a spark plug of a comparative example, (b) a diagram showing the results of an evaluation test of a comparative example, and (c) a diagram showing the results of an evaluation test of a test example. The bottom view of the spark plug in the modification 1. FIG. FIG. 6 is a partially enlarged cross-sectional view taken along line VI-VI in FIG. 5 ; The bottom view of the spark plug in Embodiment 2. FIG. FIG. 8 is a partially enlarged cross-sectional view taken along line VIII-VIII in FIG. 7 ; FIG. 8 is a partially enlarged cross-sectional view taken along line IX-IX in FIG. 7 ; The bottom view of the spark plug in Embodiment 3. FIG. FIG. 11 is a partially enlarged side view of the spark plug viewed from the XI direction in FIG. 10; FIG. 11 is a partially enlarged side view of the spark plug viewed from direction XII in FIG. 10; The bottom view of the spark plug in Embodiment 4. FIG. FIG. 10 is a bottom view of the spark plug in Modification 2; FIG. 11 is a bottom view of a spark plug in Modified Mode 3; The bottom view of the spark plug in modification 4. FIG. FIG. 17 is a partially enlarged cross-sectional view taken along line XVI-XVI in FIG. 16;

(Embodiment 1)
An embodiment of a spark plug will be described with reference to FIGS. 1 to 4. FIG.
As shown in FIG. 1, the spark plug 1 of this embodiment includes a pre-chamber 2 located on the tip end side Y1 in the axial direction of the plug, a pre-chamber forming portion 30 forming the pre-chamber 2, and a tip portion within the pre-chamber 2. and a center electrode 10 on which 11 is located.
A plurality of injection holes 35 for communicating the sub chamber 2 with the main combustion chamber 3 are formed in the sub chamber forming portion 30 .
Center lines L1 and L2 of at least two injection holes 351 and 352 of the plurality of injection holes 35 intersect each other within the main combustion chamber 3 .

The spark plug 1 of this embodiment will be described in detail below.
As shown in FIG. 1, a spark plug 1 of this embodiment is attached to a cylinder head 101 of an internal combustion engine so that the tip thereof is exposed to a main combustion chamber 3 of the internal combustion engine. As shown in FIG. 2, the spark plug 1 has a tubular housing 40 whose longitudinal direction is the axial direction Y of the plug. A cylindrical insulator 50 is arranged coaxially with the housing 40 in the housing 40 . A sub-chamber forming portion 30 that forms the sub-chamber 2 is provided on the tip end side Y1 of the housing 40 in the axial direction of the plug. The auxiliary chamber forming portion 30 is formed as a component separate from the housing 40 . A fitting portion 33 is formed on the plug axial direction base end side Y2 of the auxiliary chamber forming portion 30, and a fitted portion 43 formed on the plug axial direction tip side Y1 of the housing 40 is formed on the fitting portion 33. The pre-chamber forming portion 30 is attached to the housing 40 in a mating manner. In this embodiment, the housing 40 and the pre-chamber forming portion 30 are formed separately, but instead of this, they may be integrally formed as one component. Also, the auxiliary chamber forming portion 30 may be formed integrally with the cylinder head 101 .

As shown in FIG. 2 , the center electrode 10 is arranged inside the insulator 50 coaxially with the insulator 50 . A tip portion 11 of the center electrode 10 on the tip side Y1 in the axial direction of the plug is exposed in the auxiliary chamber 2 . Inside the sub chamber 2 , a ground electrode 15 is provided on the inner surface of the sub chamber 2 at the bottom portion 31 of the sub chamber forming portion 30 . In this embodiment, the ground electrode 15 is erected on the central axis 10a of the plug, and the tip 16 of the ground electrode 15 faces the tip 11 of the center electrode 10 with a predetermined distance therebetween. A discharge gap G is formed.

As shown in FIGS. 2 and 3 , a plurality of injection holes 35 are formed in the bottom portion 31 of the sub chamber forming portion 30 . In this embodiment, the injection holes 35 include a first injection hole 351 and a second injection hole 352 . As shown in FIG. 2, the first injection hole 351 is formed to penetrate the bottom portion 31 along the center line L1. Here, the center line L1 of the first injection hole 351 is an imaginary line passing through the center of the opening of the first injection hole 351 on the inner side of the sub chamber 2 and the center of the opening on the main combustion chamber 3 side.

As shown in FIGS. 2 and 3, the second injection hole 352 is provided at a position symmetrical to the first injection hole 351 with respect to the plug central axis 10a. The second injection hole 352 is formed to penetrate the bottom portion 31 along the center line L2. The center line L1 and the center line L2 intersect each other at a first intersection point P1 located within the main combustion chamber 3 . In this embodiment, the center line L1 and the center line L2 also intersect the plug center axis 10a at the first intersection point P1.

(Evaluation test)
Next, an evaluation test was conducted based on the simulation of flame ejection.
In the evaluation test, the spark plug 1 of the present embodiment was used as a test example, and the spark plug 9 shown in FIG. 4A was used as a comparative example. In the ignition plug 9 of the comparative example, injection holes 91 and 93 are formed in the bottom portion of the pre-chamber forming portion 30 . The centerlines L1' and L2' of the injection holes 92 and 91 do not cross each other. The test conditions were fuel type propane (air-fuel ratio: stoichiometric), pressure 2 MPa, and ignition energy 50 mJ.

As shown in FIG. 4B, in the ignition plug 9 of the comparative example, the flames ejected from the injection holes 91 and 92 are translated and are less likely to interfere with each other. Therefore, flame disturbance in the main combustion chamber 3 is small, and flame growth in the main combustion chamber 3 is small. On the other hand, in the ignition plug 1 of the test example shown in FIG. turbulence has increased, and the flame has greatly grown and expanded in the main combustion chamber 3 .

Next, the effects of the spark plug 1 of this embodiment will be described in detail.
In the spark plug 1 of the present embodiment, center lines L1 and L2 of at least two injection holes 351 and 352 provided in the sub chamber forming portion 30 intersect each other within the main combustion chamber 3 . Therefore, the flames ejected from the injection holes 351 and 352 collide with each other inside the main combustion chamber 3 . As a result, compared to the case where the flames ejected from the respective nozzle holes 351 and 352 move in parallel within the main combustion chamber 3, the disturbance of the flames inside the main combustion chamber 3 becomes greater, and as a result, the flames inside the main combustion chamber 3 , the area ignited by the flame can be expanded, the combustion speed in the main combustion chamber 3 can be increased, and the ignitability can be improved. Note that the center line L1 and the center line L2 need only substantially intersect. This embodiment also includes the case where the flames collide with each other and the disturbance of the flame becomes large.

In this embodiment, the first injection holes 351 and the second injection holes 352 are provided as the plurality of injection holes 35, but the present invention is not limited to this, and three or more injection holes 35 may be provided. For example, in Modification Mode 1 shown in FIGS. The third injection hole 353 and the fourth injection hole 354 are configured such that their respective center lines L3 and L4 intersect at the first intersection point P1. As shown in FIG. 6, the first injection hole 351 to the fourth injection hole 354 are positioned on a virtual circle C1 when viewed from the axial direction Y of the plug. The centerlines L3 and L4 of the third injection hole 353 and the fourth injection hole 354 are perpendicular to the centerlines L1 and L2 when viewed from the axial direction Y of the plug. Also in the modified form 1, the same effects as those of the first embodiment are obtained.

Note that the spark plug 1 of the present embodiment may have a configuration for injecting fuel into the auxiliary chamber 2 . Further, although the spark plug 1 of the present embodiment is configured to generate air discharge in the discharge gap G, it may be configured to generate creeping discharge in the discharge gap G instead. In either case, it is possible to obtain the same effect as that of the present embodiment.

As described above, according to the present embodiment, it is possible to provide a spark plug capable of improving ignitability.

(Embodiment 2)
As shown in FIGS. 7, 8, and 9, the ignition plug 1 of Embodiment 2 includes first to fourth injection holes 351 to 354, like Modification 1. FIG. In this embodiment, as shown in FIG. 8, the center line L3 of the third injection hole 353 and the center line L4 of the fourth injection hole 354 intersect at the second intersection point P2 located inside the main combustion chamber 3. are doing. As shown in FIGS. 8 and 9, the second point of intersection P2 is positioned farther from the spark plug 1 than the first point of intersection P1 on the plug central axis 10a. Other configurations are the same as those of Embodiment 1 and Modification 1, and in Embodiment 2, the same reference numerals as those of Embodiment 1 and Modification 1 are given, and description thereof is omitted.

Therefore, in the second embodiment, the plurality of injection holes 35 are composed of a first injection hole group 35A composed of a plurality of injection holes 351 and 352 whose respective center lines L1 and L2 intersect with each other at the first intersection point P1, and a second injection hole group 35B consisting of a plurality of injection holes 353, 354 whose respective centerlines L3, L4 intersect with each other at a second intersection point P2, where the first intersection point P1 and the second intersection point P2 are , are positioned at different positions. As a result, the nozzle holes 351 and 352 of the first nozzle hole group 35A and the nozzle holes 353 and 354 of the second nozzle hole group 35B facilitate flame turbulence and enable ignition in a wider range. , the combustion speed can be further increased to further improve ignitability. It should be noted that the same effects as those of the first embodiment are also obtained in the second embodiment.

Further, in the second embodiment, the first intersection point P1 and the second intersection point P2 are located at different positions in the axial direction Y of the plug. As a result, turbulence of the flame is promoted in the main combustion chamber 3 and the flame can be ignited in a wider range, so that the combustion speed can be further increased and the ignitability can be further improved.

(Embodiment 3)
In the third embodiment, as shown in FIGS. 10, 11 and 12, a first injection hole 351 and a second injection hole 352 are provided. As shown in FIGS. 10 and 12, the center line L1 of the first injection hole 351 and the center line L2 of the second injection hole 352 extend from the inside of the auxiliary chamber 2 toward the main combustion chamber 3 when viewed from the axial direction Y of the plug. It inclines so that it may separate from the plug central axis 10a as it goes. As shown in FIG. 10, when viewed from the axial direction Y of the plug, a first intersection point P1 where the center line L1 of the first injection hole 351 and the center line L2 of the second injection hole 352 intersect is the pre-chamber forming point. It is positioned so as not to overlap with the portion 30 . Other configurations are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are used in the third embodiment, and the description thereof is omitted. Also, the spark plug 1 of the third embodiment has the same effects as those of the first embodiment.

(Embodiment 4)
In the third embodiment, the first injection hole 351 and the second injection hole 352 are provided. In the fourth embodiment, as shown in FIG. In addition, a third injection hole 353 and a fourth injection hole 354 are provided. The third injection hole 353 and the fourth injection hole 354 are formed in the same manner as the first injection hole 351 and the second injection hole 352, and the center line L3 of the third injection hole 353 and the center of the fourth injection hole 354 A second intersection point P2 where the line L4 intersects is provided at a different position from the first intersection point P1.

Therefore, in the fourth embodiment, the plurality of injection holes 35 are composed of a first injection hole group 35A composed of a plurality of injection holes 351 and 352 whose respective center lines L1 and L2 intersect with each other at the first intersection point P1, and a second injection hole group 35B consisting of a plurality of injection holes 353, 354 whose respective centerlines L3, L4 intersect with each other at a second intersection point P2, where the first intersection point P1 and the second intersection point P2 are , are positioned at different positions. As a result, the nozzle holes 351 and 352 of the first nozzle hole group 35A and the nozzle holes 353 and 354 of the second nozzle hole group 35B facilitate flame turbulence and enable ignition in a wider range. , the combustion speed can be further increased to further improve ignitability. It should be noted that the same effects as those of the first embodiment are also obtained in the third embodiment.

Although the positions of the first intersection point P1 and the second intersection point P2 are not limited, in the fourth embodiment, the first intersection point P1 and the second intersection point P2 are symmetrical with respect to the plug central axis 10a. in position.

In the fourth embodiment, the first injection hole group 35A and the second injection hole group 35B are provided. A third injection hole group 35C consisting of 356 may be provided. The fifth injection hole 355 and the sixth injection hole 356 are formed in the same manner as the first injection hole 351 and the second injection hole 352, and the center line L5 of the fifth injection hole 355 and the center line of the sixth injection hole 356 A third intersection point P3 where L6 intersects is provided at a position different from that of the first intersection point P1 and the second intersection point P2. As a result, according to the modified embodiment 2, flame turbulence can be promoted in a wider range than in the case of the fourth embodiment, so that the combustion speed can be further increased and the ignitability can be further improved. It should be noted that the second modification also has the same effect as the first embodiment.

As shown in FIG. 14, when viewed from the axial direction Y of the plug, a first imaginary line segment M1 connecting the first intersection point P1 and the plug center axis 10a, and a second intersection point P2 and the plug center axis 10a are defined. The angle θ1 formed by the connecting second virtual line segment M2 is in the range of 45° to 180°, preferably in the range of 90° to 120°. there is As a result, the first intersection point P1 and the second intersection point P2 are spaced apart appropriately in the circumferential direction around the center of the plug center axis 10a. It is possible to further increase the combustion speed and further improve the ignitability.

The angle θ2 formed by the third virtual line segment M3 connecting the third intersection point P3 and the plug central axis 10a and the second intersection point P2, and the angle θ2 between the third virtual line segment M3 and the first virtual line segment The angle θ3 formed with M1 can also be the same as θ1, and θ2 and θ3 are set to 120° in the third modification. As a result, in the circumferential direction around the center of the plug central axis 10a, the flame is ejected in a well-balanced manner and flame turbulence is promoted, so that ignitability can be further improved.

15 has a configuration in which injection holes 361 to 364 equivalent to the injection holes 351 to 354 of the modification 1 shown in FIG. 5 are combined with the construction of the modification 2 shown in FIG. Also in the modified form 3, the same effect as the modified forms 1 and 3 can be obtained.

16 and 17, a concave portion 37 is formed in the auxiliary chamber forming portion 30 so as to be concave toward the plug axial direction base end side Y2 on the plug axial direction tip side Y1. The concave portion 37 has a conical shape centered on the plug central axis 10a. In the concave portion 37, the most proximal position 37a located on the plug axial direction proximal end side Y2 is located on the plug central axis 10a. The concave portion 37 is formed with first to fourth injection holes 351 to 354 in the same manner as in Modification 1 described above. Other configurations are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are given, and the description thereof is omitted. Also in the fifth modification, the same effect as in the first embodiment is obtained.

The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention.

Reference Signs List 1 Spark plug 2 Pre-chamber 3 Main combustion chamber 10 Center electrode 10a Center axis of plug 11 Tip end 30 Pre-chamber forming part 35, 351 to 354, 361 to 364 Injection Holes 35A to 35C... injection hole group G... discharge gap L1 to L6... center line M1 to M3... virtual line segment

Claims (4)

A pre-chamber (2) located on the tip side in the axial direction of the plug, a sub-chamber forming portion (30) forming the sub-chamber (2), and a center electrode (10) having a tip portion (11) located in the sub-chamber. and
A plurality of injection holes (35) are formed in the sub-chamber forming portion for communicating the sub-chamber with the main combustion chamber (3),
The spark plug (1), wherein at least two injection holes (351, 352) of the plurality of injection holes have respective centerlines (L1, L2) that intersect each other in the main combustion chamber. a first injection hole group (35A) comprising a plurality of injection holes (351, 352) whose respective center lines (L1, L2) intersect with each other at a first intersection point (P1); a second injection hole group (35B) consisting of a plurality of injection holes (353, 354) whose respective centerlines (L3, L4) intersect each other at a second intersection;
2. The spark plug according to claim 1, wherein said first intersection point and said second intersection point are positioned at different positions. 3. The spark plug according to claim 2, wherein said first intersection point and said second intersection point are located at different positions in the axial direction of the plug. When viewed from the axial direction of the plug, a first virtual line segment (M1) connecting the first intersection point and the plug central axis, and a second virtual line connecting the second intersection point and the plug central axis. The spark plug according to claim 2 or 3, wherein the angle with the minute (M2) is within the range of 45° to 180°.

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